The invention relates to a pump arrangement, in particular magnetic clutch pump arrangement. The pump arrangement has an interior space formed by a pump casing a containment can which hermetically seals off a chamber surrounded by said containment can with respect to the interior space formed by the pump casing, an impeller shaft which can be driven in rotation about an axis of rotation, an impeller which is arranged on one end of the impeller shaft, an inner rotor arranged on the other end of the impeller shaft, an auxiliary impeller arranged in the chamber, and an outer rotor which interacts with the inner rotor.
German patent document no. DE 27 54 840 A1 has disclosed a magnetic clutch pump arrangement of said type with an auxiliary impeller. The auxiliary impeller is of disk-shaped construction and is equipped with radial bores. However, said embodiment, with regard to its efficiency, constitutes an inefficient impeller or delivery variant, and lowers the overall efficiency of the pump arrangement. Furthermore, a not inconsiderable level of outlay is required to produce the auxiliary impeller.
It is the object of the invention to provide a magnetic clutch pump arrangement with a forced-lubrication flow drive which is simple to produce and which exhibits improved efficiency.
The object of the invention is achieved in that the auxiliary impeller is fastened to the inner rotor.
Since the auxiliary impeller is fastened by way of its open side to that face side of the inner rotor which faces toward the base of the containment can, it is possible for the advantages of a closed channel-type impeller to be utilized by way of an open impeller, which is much easier to produce. Furthermore, the impeller does not have a hub and is easy to assemble and disassemble.
In one refinement, the containment can has a main body with an open side and with a side which is situated opposite the open side and which is closed by way of a domed base, and the auxiliary impeller has a rear shroud, whose outer surface facing toward the base of the containment can has a domed form.
By virtue of the fact that the domed form of the outer surface of the rear shroud substantially corresponds to the domed form of the base of the containment can, the dead space that is normally spanned by the domed base of the containment can is filled, whereby no additional axial structural space required by the magnetic clutch is taken up. Furthermore, the pressure resistance of the containment can is not unnecessarily reduced.
To improve the flow guidance of the medium as it enters a fluid inlet region of the auxiliary impeller, a paraboloid-like elevation is ideally provided in the center of the rear shroud.
In a further refinement, it is provided that, on the rear shroud, at a radial distance from the elevation, there are formed multiple raised portions which form vanes and corresponding impeller channels of the auxiliary impeller.
In a further refinement, it is proposed that the impeller channels have a channel base which is similar in form to a rampant three-center arch. This leads to an improvement in flow guidance.
In a further refinement of the invention, it is provided that the upper side of the vanes opposite the rear shroud, has a step close to the channel inlet edge. The step serves as an abutment shoulder and centering device for precise alignment of the auxiliary impeller fastened to the inner rotor.
For simple and inexpensive production, the impeller shaft and the inner rotor form a cover shroud, situated opposite the rear shroud, of the auxiliary impeller.
In a further advantageous refinement, in the raised portions which form the vanes, there are formed further impeller channels which extend in a radial direction from the outer lateral surface as far as a point close to the step.
To improve the flow guidance of the medium, the further impeller channels have a channel base which, at least in part, has a domed form which corresponds substantially to the domed form of the outer surface of the rear shroud.
According to the invention, the impeller shaft has an axial channel which is connected to the fluid inlet region of the auxiliary impeller.
In the context of the invention, it is proposed that, in a further embodiment, in the inner rotor, there are provided fluid channels which issue into the further impeller channels of the auxiliary impeller.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.